This invention relates to the field of biomedical testing, and more particularly to the transport, handling and processing of biomedical sample holders such as microplates. Microtiter plates, commonly known as "microplates", facilitate the simultaneous testing (or other processing) of a large number of individual biomedical samples. Microplates have been in common use for decades with a predominant format being a molded plastic plate having 96 sample wells in an 8.times.12 rectangular array. Typical well volumes are 200 or 300 microliters, depending upon the manufacturer and model of plate, although other volumes may be provided for specific uses. A proposed standard, designated "Microplate 96-Well Standard" (MP96) has been promulgated by The Society for Biomolecular Screening, as published in Journal of Biomolecular Screening, Volume 1, Number 4, 1996, the disclosure of which is incorporated herein by reference. A microplate which meets the general dimensional requirements of the standard is designated MP96-3. Typically, each microplate manufacturer will also provide a compatible lid. A typical lid comprises a generally rectangular flat planar top surrounded by a flange depending from the top along its sides and edges.
Automated handling of microplates has become an important criterion in their design. It is therefore desirable to provide a microplate lid configuration that facilitates use with automation. Specifically, it is desirable to provide a lid that facilitates automatic stacking and unstacking of lidded microplates, automatic stacking and unstacking of lids without microplates, and automated installation and removal of lids from microplates.